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XPS study of Pb(II) adsorption on $$gamma$$-Al$$_{2}$$O$$_{3}$$ surface at high pH conditions

Yoshida, Takahiro; Yamaguchi, Tetsuji ; Iida, Yoshihisa ; Nakayama, Shinichi 

Pb(II) adsorption on $$gamma$$-Al$$_{2}$$O$$_{3}$$ at high pH condition (11 $$<$$ pH $$<$$ 13) was studied in NaNO$$_{3}$$ solutions. With increasing pH from 11, Pb(II) uptake by $$gamma$$-Al$$_{2}$$O$$_{3}$$ was decreased regardless to sodium concentration (0.1 and 1.0 M). XPS spectra showed binding energy of adsorbed Pb (4f) had no dependence on pH and adsorption density and was higher than that of orthorhombic yellow PbO and Pb(NO$$_{3}$$)$$_{2}$$. Molecular orbital (MO) calculation revealed lowest unoccupied molecular orbital (LUMO) energy of Pb(OH)$$_{3}$$$$^{-}$$ was about 6 eV higher than that of Pb(OH)$$_{2}$$, and suggested chemical reactivity of Pb(OH)$$_{3}$$$$^{-}$$ with deprotonated surface hydroxyl ligand [$$equiv$$AlO$$^{-}$$] was expected to be less than that of Pb(OH)$$_{2}$$. Although Pb(II) is adsorbed on $$gamma$$-Al$$_{2}$$O$$_{3}$$ as inner-sphere surface complex, bonding between Pb(II) and $$gamma$$-Al$$_{2}$$O$$_{3}$$ shows less covalent nature.



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Category:Nuclear Science & Technology



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